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Oil Filter Change questions: How does the rubber ring work?

When changing the spin-type can oil filter, I was trained to ALWAYS apply a fingertip swipe of fresh oil around the rubber ring gasket before installing it. Supposedly, this helps to make a good seal and prevent leaks.

But after years of doing this out of habit, it occurs to me that petroleum rots rubber... (and that's the reason why oil-based lubes are NEVER used with laytex condoms, and other rubber products).

So, what's the real story here? Why is a rubber gasket ring used when exposed to high heat, pressure and oil circulation? Or am I missing something obvious here?

Any mechanics out there who could comment? Thanks.

O my captain asked in Cars & Motorcycles 10 months ago | Report

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    I believe most of the "rubber" seals in car engines are in fact chemically closer to Neoprene, and far more resilient than natural rubber.

    The layer of oil you spread on the new gasket keeps it from stretching or bunching up when you tighten the filter, thus improving the seal.

    And anyway, there's 60 psi of hot motor oil inside of that gasket most of the time. The thin film you spread on with your finger is a drop in the bucket.

    Lack Thereof answered in Cars & Motorcycles 10 months ago | Report
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    Firstly, the layer of rubber you're talking about on a condom is probably about a thousand times thinner than the rubber seals in your car. Secondly, the problems with condom failure with petroleum lube are more related to the petroleum lubes losing lubricity in wet environments, which in combination with weakened latex can cause ripping when subjected to motion.

    Also consider that the oil filter o-ring gets changed a few times a year, stuff like the valve stem seals are subjected to much higher heat, some friction and they last more-or-less the life of the engine. So quit worrying and definitely do put that layer of oil on the filter o-ring. You're asking for leaks if you don't.

    Jack answered in Cars & Motorcycles 10 months ago | Report
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  • Meansceneprod-gothgirl7872_small
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    Not a mechanic but I do know a thing or two about polymers. I'm too lazy to research it right now and make sure but I'd bet dollars to o-rings that the obvious thing you're missing here is that the gasket on oil filters is not made from latex but from PTFE, polyurethane, nylon, or some other petroleum based polymer.

    Very few "rubber" items you find these days here in the U.S.A. actually contain latex and I'd be hard pressed to think of a worse place to use latex than an oil filter gasket, Fram has likely considered this already.

    goth jenny answered in Cars & Motorcycles 10 months ago | Report
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